The major objective in this research is to make significant contributions to organic chemistry and medicine through synthetic studies on physiologically active natural and man-made organic compounds, including 1. the total synthesis and conformational analysis of the marine natural product palytoxin, 2. the synthesis and conformational analysis of oligosaccharides and their carbon analogues such as cellobiose, maltose, human blood group antigens, and sucrose, 3. the synthesis and conformational analysis of semi-synthetic polyether antibiotics, 4. the development of organic solvent soluble 310-helical oligopeptides, 5. semi- synthetic aequorins as a tool of the determination of local calcium concentration on the intact cells, and 6. enantioselective synthesis of saxitoxins and gonyautoxins. We believe that the power of organic chemistry is most effectively extended by challenging complex systems, and much of the progress of medicine critically depends upon the extension of the power of organic chemistry. It is also our specific objective to develop practical and efficient syntheses of certain natural products and their analogues which have high physiological activity, but are not available in appreciable amount from natural sources. These studies are again expected to stimulate the progress in medicine.